Dehumidification can be important for a variety of applications including comfort, health, industry and manufacturing, defrosting or defogging of windows, collection of water from the air for drinking or other uses, maintenance of frozen food, preservation of building materials and other objects, and prevention of mold, dust mites, and other harmful pests.
Referring to FIG. 1A, in a vapor compression cycle dehumidification system 20, moisture is removed by cooling air 22 to be dehumidified below its dew point, causing moisture to condense out of the air. The air is cooled by a refrigerated cooling coil (an evaporator 24) and moisture condenses on the surface of the coil and drains off the coil by gravity into a condensate pan 26 and is sent to a drain 28. The cooled air 30 is then reheated by passing through a condenser 32 (cooling the condenser in the process).
Referring to FIG. 1B, the performance (both the efficiency and the amount of moisture removed for a given refrigerant compressor capacity) can be improved by using the cooled air 30 leaving evaporator 24 to pre-cool air 22 before it enters the evaporator, i.e., by recuperating, reducing the amount of cooling that is done by the evaporator and a compressor 34. As shown, an upstream coil 36 and a downstream coil 38 relative to evaporator 24 provide the recuperative pre-cooling, with the heat that is removed from incoming air 22 transported by heat pipes 40 to the downstream coil, where it is transferred to cooled dry air 30 leaving the evaporator.
Other methods of recuperation include pumping an independent heat transfer fluid between an incoming air stream and a post evaporator air stream, and directly exchanging heat between an incoming air stream and the air stream leaving the evaporator without the use of a heat transfer fluid.